Ciguatoxin is the causative agent of a human neurological disorder known as ciguatera. Ciguatera poisoning results from the ingestion of a number of tropical reef fishes, e.g. snappers and groupers. Ciguatoxin has been isolated as an apparently homogeneous non-crystalline entity from the muscle of the moray eel, Gymnothorax javanicus, in a yield of about 100 ppb. We shall attempt to isolate ciguatoxin in sufficient quantity to allow full elucidation of its molecular structure by physical and chemical methods. We shall try to crystallize ciguatoxin or a derivative of the toxin suitable for single crystal X-ray determination. Parallel with this approach we shall carry out structural studies by C13 and H1 nuclear magnetic resonance spectrometry; by mass spectrometry; and by chemical transformations to moieties of low molecular weight.